From the outside, the Tea Party movement appears to be powerfully united despite its amorphous and slightly anarchic nature. But behind the impressive facade it is riven by rivalries and conflicting agendas.

Two of the most high-profile and influential female leaders of the movement are in legal dispute. The bitter lawsuit has been running for a year, although the protagonists appear to have much more in common with each other than in contrast.

Amy Kremer, who chairs the Tea Party Express, and Jenny Beth Martin, national co-ordinator of the Tea Party Patriots, both come from Atlanta, Georgia. They are both touring the US on separate battle buses rallying the conservative troops ahead of next Tuesday's midterm elections.

They were both present at the creation of the Patriots, an umbrella organisation that acts as a social network for up to 2,800 loosely affiliated local Tea Parties. Kremer says the Patriots were founded in her living room at home in suburban Atlanta.

Yet these days the two women communicate only through lawyers. Neither would give the Guardian details of the specific complaints they have against the other, but the fallout appears to have originated from Kremer's decision to begin working with the Tea Party Express, a similar affiliation of local groups headquartered in Sacramento, California.

Last year Kremer left the Patriots to devote herself to the Express. In November the Patriots obtained an injunction in the Atlanta courts ordering her to stop using the Patriots' "intellectual property" in her campaign literature and events. That included the name and the website of the Tea Party Patriots, its mailing and email lists and databases.

"My mother always told me if you can't work with somebody, you work around them," Kremer told the Guardian. She said the Patriots were "continuously kicking Tea Party Express, they are always saying something negative. We just don't play that way. We are focused on our mission and we don't need to tear down another organisation in order to build ourselves up. If they want to focus their efforts on a conservative firing squad, so be it."

Kremer said that in her view the underlying cause of the dispute was the desire of the Tea Party Patriots to own the movement. "There are groups out there that want to be the leader of this movement. They want to be the only Tea Party group. But there is no leader, there is no one organisation or one person or couple of people that are the leaders."

Martin said she never commented on active legal issues, although she confirmed the lawsuit was ongoing. "All I can say is that our 2,800 affiliated local groups around the country are voluntarily united around our principles of fiscal responsibility and free markets."

Attempts by groups or individuals to marshal the energy of the Tea Parties and give them a structure have invariably prompted revolts from the rank and file. In February a Nashville lawyer, Judson Phillips, held what he billed as the first national Tea Party convention. Other Tea Party leaders and bloggers cried foul, registering their disdain for the idea of giving this bottom-up surge of conservatism a central voice. They also objected to the $549 price of tickets to the event and the reported $100,000 speaking fee given to Sarah Palin.

Kate Zernike, the author of Boiling Mad: Inside Tea Party America, said the scrap in Nashville was typical of the sorts of resentments and infighting that has erupted spasmodically across the movement. She said the clashes did not appear to have hurt the movement or lessened its power to motivate voters.

"If anything, the infighting has just proved that the Tea Parties are not controlled by some grand wizard behind a curtain but are a genuine grassroots movement with energy rising up from below," Zernike said.

Race has been one lightning rod for disagreement between Tea Parties. In July the Tea Party Express was expelled from the National Tea Party Federation, a network of about 80 groups, over the incendiary comments of one of its vice-chairs, Mark Williams. The federation objected to a blog featuring racially-charged jokes.

"Dear Mr Lincoln, We Coloreds have taken a vote and decided that we don't cotton to that whole emancipation thing," the blog began.

Christina Botteri, a founding member of the federation, said they had no choice but to take action. "Our members were offended by what he wrote. The Tea Party movement is much more important than this kerfuffle and we couldn't do nothing."

Deborah Johns, who was vice-chair of the Tea Party Express alongside Williams, said she quit the group in protest at his blog. The Express has countered that she was terminated from her position within the organisation "with cause", although it has not revealed the precise reason for her dismissal.

Sol Russo, a Republican political consultant who is the brains behind the Tea Party Express, defended Williams. "He is a radio host, and making controversial jokes is what radio hosts do," he said.

• This article was amended on 29 October. The use of the term martial was used instead of marshal. This has been corrected.

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